There are some health concerns regarding organic UV filters used in sunscreens, such as oxybenzone or avobenzone. However, they provide vital protection against harmful UV radiation. Reducing direct skin contact could reduce the health risks of these compounds. This could be achieved, e.g., by incorporating the UV filters into nanoparticle carriers.

Douglas Richard Hayden, Universiteit Utrecht, The Netherlands, and colleagues have synthesized size-tunable ethyl cellulose nanoparticles (ECNPs) and used them as carriers for three different commercial organic UV filters (oxybenzone, avobenzone, and octinoxate). The team prepared ECNPs of different sizes using a modified antisolvent precipitation technique. Coprecipitation was used to encapsulate the different UV filters in the nanoparticles.

The size of the nanoparticles could be tuned in the range of 50–165 nm by varying the amount of ethyl cellulose used in the synthesis. Sizes below 100 nm are particularly useful for sunscreens because the resulting formulations appear transparent when applied on the skin. All three UV filters could be encapsulated efficiently, with maximum loadings of 54.5 wt% for octinoxate, 13.8 wt% for oxybenzone, and 7.8 wt% for avobenzone. The photostability of the UV filters was not affected by the encapsulation. The ECNPs themselves are biobased and biocompatible, and they can be used in various solvent systems for different sunscreen formulations.

• Size and Optically Tunable Ethyl Cellulose Nanoparticles as Carriers for Organic UV Filters,
  Douglas Richard Hayden, Heleen Kibbelaar, Arnout Imhof, Krassimir Petkov Velikov,
  ChemNanoMat 2018.
  https://doi.org/10.1002/cnma.201700332